How to publish ASP.NET Core Web API in .NET 7 to Azure if it expects Startup.cs file?

Question

I'm trying to publish my ASP.NET Core 7 Web API to Azure but whenever I try to do so I get this error message:

Publish has encountered an error.
Be sure that the Startup.cs for your application is calling AddSwaggerGen from within ConfigureServices in order to generate swagger file. Visit https://go.microsoft.com/fwlink/?LinkId=2131205&CLCID=0x409 for more information.

A diagnostic log has been written to the following location: "C:\Users\cvale\AppData\Local\Temp\tmp4709.tmp"

.NET 7 (and 8) don't have Startup.cs and do everything in Program.cs. So I have AddSwaggerGen() in my Program.cs, yet I'm still getting the error when trying to publish.

Has anyone else run into this problem and been able to fix it? Thanks in advance!

I tried placing builder.Services.AddSwaggerGen() in Program.cs

Answer 1

When I tried deploying .NET 7 WEB API to Azure App Service, even I faced the issue. I have added the below code to my program.cs file.

app.UseSwagger();
app.UseSwaggerUI(x =>
{
    x.SwaggerEndpoint("/swagger/v1/swagger.json", "Web API V1");
if(app.Environment.IsDevelopment())
    x.RoutePrefix = "swagger"; // For localhost
else
    x.RoutePrefix = string.Empty;
//  For azure
}
);

Then, I am able to deploy the App successfully.

My complete Program.cs file

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddControllers();
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

var app = builder.Build();
app.UseSwagger();
app.UseSwaggerUI(x =>
{
    x.SwaggerEndpoint("/swagger/v1/swagger.json", "Web API V1");

if(app.Environment.IsDevelopment())
    x.RoutePrefix = "swagger"; 
else
    x.RoutePrefix = string.Empty;
}
);

app.UseSwagger();
app.UseHttpsRedirection();
app.UseAuthorization();
app.MapControllers();
app.Run();

Local output:

I deployed my Web API using the Visual Studio Publish option.

Successful Deployment

Azure Web App Output :